title: Molecular characterization of an oxidosqualene cyclase that yields shionone, a unique tetracyclic triterpene ketone of Aster tataricus.
abstract: Shionone is the major triterpenoid component of Aster tataricus possessing a unique all six-membered tetracyclic skeleton and 3-oxo-4-monomethyl structure. To clarify its biosynthetic process, an oxidosqualene cyclase cDNA was isolated from A. tataricus, and the function of the enzyme was determined in lanosterol synthase-deficient yeast. The cyclase yielded ca. 90% shionone and small amounts of β-amyrin, friedelin, dammara-20,24-dienol, and 4-epishionone and was designated as a shionone synthase (SHS). Transcripts of SHS were detected in A. tataricus organs, confirming its involvement in shionone biosynthesis. SHS was shown to have evolved in the Asteraceae from β-amyrin synthase lineages and acquired characteristic species- and product-specificities.
authors.affiliation: Department of Applied Biological Sciences, Nihon University, Fujisawa, Kanagawa, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Sawai
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Uchiyama
authors.forename: Syuhei
authors.initials: S
authors.lastname: Mizuno
authors.forename: Toshio
authors.initials: T
authors.lastname: Aoki
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Akashi
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Ayabe
authors.forename: Takeyoshi
authors.initials: T
authors.lastname: Takahashi
mesh_terms: D000595:Amino Acid Sequence; D031173:Aster Plant / Q000201:enzymology* / Q000235:genetics; D003001:Cloning, Molecular; D019143:Evolution, Molecular; D018506:Gene Expression Regulation, Plant; D006801:Humans; D019751:Intramolecular Transferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D014315:Triterpenes / Q000378:metabolism*
chemical_list: D014315:Triterpenes; C055671:shionone; D019751:Intramolecular Transferases; C021924:lanosterol synthase